Dr. Eric Challgren and his colleague, Dr. Gregory Wilmoth, are widely recognized by patients and fellow practitioners for their expertise in Mohs surgery. Mohs is broadly recognized as the skin cancer treatment with the highest cure rate—in the range of 99 percent. Before coming to Raleigh, Dr. Wilmoth was with a large dermatology group in Jacksonville, Florida. “It was in this setting that I got extensive experience in treating skin cancer, including nearly every-day skin cancer surgery,” he says. He had intensive training in Mohs surgery in his residency years, and often performed the
Mohs procedure while in Florida. And Dr. Challgren had extensive training in Mohs surgery in his residency years and the decade following.
Mohs surgery—named after the doctor who developed it—has been in use since the 1930s. “It differs from other skin cancer treatments in that it permits the immediate and complete microscopic examination of the removed cancerous tissue, so that all ‘roots’ and extensions of the cancer can be eliminated,” says Dr. Challgren.
“Some skin cancers,” he notes, “can be deceptively large—far more extensive under the skin than they appear to be from the surface. These cancers may have ‘roots’ in the skin, or along blood vessels, nerves, or cartilage. And skin cancers that have recurred following previous treatment may send out extensions deep under the scar tissue that has formed at the site.”
“Mohs surgery is specifically designed to remove these cancers by tracking and removing these cancerous roots,” explains Dr. Challgren. “For this reason, prior to Mohs surgery it was impossible to predict precisely how much skin had to be removed. The final surgical wound could be only slightly larger than the initial skin cancer, but occasionally the removal of the deep roots of a skin cancer resulted in a sizeable wound.”
Mohs is not appropriate for all skin cancers, Dr. Challgren points out. “It is typically reserved for those skin cancers that have recurred following previous treatment, or for cancers that are at high risk for recurrence.
“Mohs is the procedure of choice for cancers located in areas such as the nose, eyelids, lips, hairline, hands, and feet.”
“It is also the procedure of choice for cancers located in areas such as the nose, eyelids, lips, hairline, hands, and feet—areas in which preservation of healthy tissue is critical for cosmetic or functional purposes. For skin cancers that are on the face or hands, or locations where there is little extra tissue to use for repair, Mohs surgery becomes an extremely important technique. For small tumors on the head and neck, for example, Mohs is appropriate because it spares tissue and it makes the final resulting scar much smaller.
“In the more common way of treating skin cancers, we check about 1 percent of the margins as we excise a tumor. For skin cancers that would be considered routine, in terms of type, size, and location, that approach is efficient and produces a cure rate of 95 percent or better; however, a large margin (over 4 mm) is taken in order to compensate for the reduced visualized margin, resulting in a larger wound defect.
“With Mohs surgery, we’re checking 100 percent of the margin and the base of the tumor. When I say ‘100 percent,’ I mean the entire periphery and the base of the tumor. For large or unusual skin cancers, and for those in difficult-to-treat locations, checking 100 percent is a very good idea. Above all else, we seek to accomplish these goals: to remove all of the cancer; to reduce the chance of recurrence to the absolute minimum, and to produce the best possible cosmetic outcome. Mohs permits us to do that.”
“We do Mohs surgery as an outpatient procedure with local anesthesia” Dr. Challgren explains. We clean and mark the area to be treated and remove the visible cancer along with a thin layer (about 1 mm) of additional tissue. The patient waits while tissue is being processed and examined. The removed tissue specimen is cut into sections, stained, and marked on a detailed diagram called a Mohs map. Tissue is frozen on a cryostat machine, and the technician removes very thin slices from the entire edge and undersurface. These slices are
then placed on slides and stained for my examination under the microscope.
“If under microscopic examination I find residual cancer, I’ll remove additional tissue as indicated by the Mohs map—only in the area where the cancer is present. This process is repeated as many times as necessary during the same treatment to locate any remaining cancerous areas within the tissue specimen. It is usually concluded between one to three stages.”
One of the great advantages of the Mohs procedure, Dr. Challgren notes, is that this information is available while the patient waits for the outcome of the examination. “When I finally see no remaining tumor in the specimen, the patient and I are ready to consider how best to repair the surgical site.”
As with all forms of surgery, a scar will remain after the skin cancer is removed and the surgical area has completely healed. “Mohs micrographic surgery, however, leaves one of the smallest possible surgical defects and resultant scars,” Dr. Challgren says. “Often, wounds allowed to heal on their own result in scars that are barely noticeable.
“We had a patient recently who had a skin cancer on the tip of her nose, which extended from one side of her nose to the other side. It was unclear where the cancer began and where it ended, so Mohs surgery was clearly the best treatment choice. “Beyond the Mohs surgery, we are able to do extensive functional and cosmetic repair work. For this patient, we went five stages to get clear margins, and in the process had to remove the skin from her nose fairly extensively. We employed standard reconstructive techniques to fix the resulting defects. In this instance, we removed skin from her forehead, and made her an attractive new nose.
“This was done as an in-office procedure with local anesthesia. When completely healed, the scar on her forehead will be small and only slightly perceptible, easily covered by makeup. And her cancer-free nose will look perfectly natural and normal, with well-hidden scarring.”